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The graphitic carbon nitride (g-C 3 N 4 ), as one photocatalyst which possess the suitable band gap, is better for modified TiO 2 and enhanced photocatalytic degradation of organic pollutants. In this work, the g-C 3 N 4 /TiO 2 were successfully prepared via directly calcined the mixture of melamine and P25. The as-prepared g-C 3 N 4 /TiO 2 photocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM) and high resolution electron microscopy (HRTEM), Raman and Fourier transform-infrared spectroscopy (FT-IR). The photocatalytic performances of g-C 3 N 4 /TiO 2 composites were investigated by degradation of ciprofloxacin. The results showed that the g-C 3 N 4 and P25 were successfully composited, and the bond of C–N was well formed, the calcined temperature for as-prepared photocatalysts and the ratio of melamine and P25 were important to the degradation rate of ciprofloxacin. When the mixture of melamine and P25 with 1:2, and calcined temperature at 600 °C, the degradation rate of ciprofloxacin could reach 95% in 60 min. The enhanced photocatalytic performances could be mainly attributed to the suitable band gap structure with heterojunction of CN-P25. Finally, the possible transferred processes of photoelectrons and photoholes were proposed. [ABSTRACT FROM AUTHOR]

Designing S-scheme heterojunctions is an effective method to improve the charge localization on the surface of photocatalysts. Their effective charge transport routes can be enhanced with the help of interfacial noble metal nanoparticles. Herein, an Ag/CuO@ZnIn 2 S 4 plasma S-scheme heterojunction with heterogeneous interfacial covalent bonds was successfully designed. The 15% Ag/CuO@ZnIn 2 S 4 has promising photocatalytic performance and stability with the highest CO and CH 4 yields of 6.9 and 54.4 µmol g−1 h−1 and CH 4 selectivity of 92.8%. It is evidenced that the photogenerated charge can be efficiently separated and transported due to the influence of both the S-scheme electron migration mode and the Cu-S covalent bond. The process is further accelerated by using precious metals as cocatalysts, which can then selectively convert CO 2 into CH 4. This research is expected to provide helpful information for engineering S-scheme heterojunction photocatalysts and investigating their charge transfer kinetics. [Display omitted] • Design of a S-scheme heterojunction to promote the separation of carriers. • Built the Cu-S bonds to accelerate the transfer of charges. • Utilizing the LSPR effect to generate hot electrons and enhance light absorption. • The Ag/CuO@ZnIn 2 S 4 photocatalysts can selectively reduce CO 2 to CH 4. [ABSTRACT FROM AUTHOR]

Wide-light absorption performance and efficient carrier separation ability are the necessary conditions for excellent photocatalytic materials. In this research, g-C 3 N 4 QDs (CN QDs) and Au nano-particles (NPs) co-modified CeO 2 /Fe 3 O 4 micro-flowers (MFs) photocatalyst (CACeF) has been prepared. CO 2 photoreduction experiments showed that the composite had obviously enhanced photoreduction activity and photocatalytic stability. The yields of CO and CH 4 over it as catalyst in 4 h is about 5 and 8 times greater than that of pure CeO 2. Photoelectrochemical tests showed that the heterojunction between CN QDs and Au NPs can greatly improve the carrier separation ability and the light-utilization efficiency of photocatalysts. Besides, the excellent electronic transmission performance of Au NPs provided a specific channel for the electron transmission, and the strong local surface plasmon resonance (LSPR) of Au NPs resulted in a lot of hot-electrons can directly take part in the CO 2 photoreduction. The synergistic effect between CN QDs and Au NPs can further enhance the photocatalytic activity of the photocatalyst. Fe 3 O 4 QDs can ensure the effective recovery and reuse of the composite without affecting the photocatalytic performance of composite. Finally, a potential photoreduction mechanism of CN QDs and Au NPs co-modified CeO 2 /Fe 3 O 4 MFs photocatalyst were discussed in total. [Display omitted] • g-C3N4 QDs/Au NPs/CeO2/Fe3O4 has been prepared for the CO2 photoreduction. • Light-absorption performance of photocatalyst has been greatly enhanced. • Au efficiently speeds up the electrons' generation efficiency in semiconductors. • Synergistic effect of CN QDs/Au NPs enhanced the photoreduction performance. • Fe3O4 QDs can ensure the recovery without affecting the photocatalytic performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • The dual-plasma enhanced g-C 3 N 4 /Pd/MoO 3-x heterojunction was fabricated for high-selectivity photocatalytic CO 2 reduction. • The g-C 3 N 4 /Pd/MoO 3-x composites revealed excellent near-infrared absorption ability. • The carrier separation efficiency was effectively improved under the synergistic effect of MoO 3-x and Pd nanosheets. • The g-C 3 N 4 /Pd/MoO 3-x S-scheme heterojunction displayed high photocatalytic performance and CO selectivity. • The S-scheme charge transfer mechanism was proposed based on UPS and ESR results. The localized surface plasmon resonance (LSPR) effect has shown significant progress in enhancing the efficiency of light absorption and separating photogenerated carriers. Herein, the dual-plasma enhanced 2D/2D/2D g-C 3 N 4 /Pd/MoO 3-x (CPM) S-scheme heterojunction photocatalysts were synthesized using the method of hydrothermal and electrostatic self-assembly for high-selectivity photocatalytic reduction of CO 2 to produce CO. The dual LSPR effect of MoO 3-x and ultrathin Pd nanosheets synergistically broadened the optical response range of the CPM composites and successfully improved the photocatalytic activity and near-infrared (NIR) performance. The optimized CPM-30 photocatalysts exhibited CO yields of 18.55 μmol g−1 with a selectivity of 96.3%. In addition, the CO yield reached 3.92 μmol g−1 after 4 h of NIR light photoirradiation. The electron spin resonance (ESR) and ultraviolet photoelectron spectroscopy (UPS) tests showed that the S-scheme heterojunctions were constructed by coupling g-C 3 N 4 /Pd nanosheets and MoO 3-x. This work will provide a reference for improving product selectivity through the design of two-dimensional composites and the utilization of plasma materials. [ABSTRACT FROM AUTHOR]

• SnS 2 atomic layer with Pt 3 Co nanoclusters have been successfully prepared. • Nanoclusters can enrich electrons, reduce barriers, and promote proton transport. • The photoelectric properties of catalysts is significantly enhanced. • The CO 2 photoreduction efficiency of the SnS 2 /Pt 3 Co catalyst is markedly improved. Poor capability of charge-holes separation and slower surface CO 2 reaction kinetics hinder photocatalytic performance. Here, SnS 2 atomic layer with Pt 3 Co alloy nanoclusters have been successfully prepared. Nanoclusters could be used as highly catalytic active sites, which not only facilitates the carrier separation and transport kinetics, but enriches electrons lowered the reaction barrier. As expected, the CO evolution rate of the champion SnS 2 /Pt 3 Co catalyst was 13.6 times higher than that of the original SnS 2 catalyst under white light irradiation. In-situ DRIFTS identifies key intermediate in the photoreduction process. In-situ XPS and DFT calculation further verifies the electron transport direction and charge density distribution at the SnS 2 /Pt 3 Co interface. Our work uncovers the role of nanoclusters in carrier separation and transport as well as proton transport, opening new chances for obtaining efficient photoreduction CO 2 property. [ABSTRACT FROM AUTHOR]

ZnO/g-C3N4 was prepared by carrying out a simple one-step calcination process. The ZnO/g-C3N4 composite was characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-Vis diffuse reflectance spectroscopy (DRS), electrochemical impedance spectroscopy (EIS), transient photocurrent responses and photo-luminescence (PL) spectroscopy. Compared with pure g-C3N4, the composite showed increased photocurrent under UV irradiation, and overall significantly improved photocatalytic performance. Photocatalytic experiments showed specifically the composite made of a ZnO-to-g-C3N4 mass ratio of 3 : 1 displaying the best catalytic performance. The yields of CO and CH4 under UV irradiation were, respectively, 13.4 times and 49.7 times that of g-C3N4. In addition, a direct Z-scheme electron transfer mechanism was proposed to possibly play a large role in reducing charge recombination and to effectively improve photocatalytic CO2 reduction. [ABSTRACT FROM AUTHOR]

A series of hamburger-like Ag@ZnO/C core–shell plasmonic photocatalysts have been synthesized via a simple solvothermal method for degradation of tetracycline (TC) under visible light irradiation, possessing high photocatalytic activity and good stability. The presence of localized surface plasmon resonance (LSPR) in the Ag core has increased the photocatalytic activity over an extended wavelength range. The plasmon-induced resonant energy transfer (PIRET) and direct electron transfer (DET) have facilitated the excitation and separation of photogenerated e−/h+ pairs, which has been further confirmed by electrochemical investigations. The presences of hydroxyl radicals (⋅OH), superoxide radicals (⋅O2−) and singlet oxygen (1O2) in the photocatalytic reaction system of Ag@ZnO/C photocatalyst have been demonstrated by electron spin resonance (ESR) measurements. All of the experiment results indicate that the ternary structure of Ag@ZnO/C can effectively enhance the photocatalytic activity. Furthermore, the effects of introduced Ag contents and carbon source dosage were researched by comparative photocatalytic experiments, and the potential structures of photodegradation products were studied by HPLC-MS. A series of hamburger-like Ag@ZnO/C plasmonic photocatalysts was synthesized. The photocatalysts exhibited great photocatalytic activity and stability, and the PIRET and DET have facilitated the excitation and separation of charges. The possible photodegradation mechanism was systematically presented and the potential structure of new photodegradation products was studied. [ABSTRACT FROM AUTHOR]

[Display omitted] • The UCN@ZIS/SWNTs composite with different V Zn concentrations was constructed for photocatalytic CO 2 reduction. • The UCN was acidified to regulate the surface-active site for CO 2 activation and H 2 O dissociation. • The SWNTs further improves the separation efficiency of photogenerated electron-hole pairs by providing charge transfer channels. • The UCN@rZIS/SWNTs composite displays excellent photocatalytic performance and CH 4 selectivity. Zinc vacancy (V Zn) concentrations were successfully regulated on the hierarchical flower spherical ZnIn 2 S 4 (ZIS) by controlling the hydrothermal temperature. The photo-electrochemical experiments indicated that the carrier separation efficiency of ultrathin-g-C 3 N 4 @ZIS/SWNTs (UCN@ZIS/SWNTs) composite with different V Zn concentrations (poor-V Zn ZIS (pZIS) and rich-V Zn ZIS (rZIS)) had an efficient improvement because of the construction of UCN@ZIS heterojunction and the multiple channels for charge transfer provided by SWNTs. In-situ FTIR results indicate that the presence of V Zn and the enriched surface-active site on UCN contributes to CO 2 activation and H 2 O dissociation. Additionally, the yield of CO and CH 4 over UCN@rZIS/SWNTs composite reached 33.7 µmol g−1 and 39.8 µmol g−1, respectively, and the selectivity of CH 4 reached 54.1 % under the synergistic effect of V Zn , the surface-active site of UCN and charge-transfer channels. This work established an ideal defect model for enhancing CO 2 photocatalytic reduction performance and product selectivity, which may provide a new way to improve photocatalytic efficiency and a better understanding of the photocatalytic reaction mechanisms. [ABSTRACT FROM AUTHOR]

A series of nebula-like ZnO/CeO 2 @HNTs heterostructure photocatalysts were synthesized via a novel one-step wet-calcination method for degradation of tetracycline (TC) under simulated solar irradiation. TEM, HRTEM, XRD, FT-IR, XPS, DRS, PL, PC, EIS and ESR techniques were applied for characterization of samples. And the potential structure of new photodegradation products was studied by HPLC–MS analysis. The characterization results revealed the enhanced photocatalytic activity of ZnO/CeO 2 @HNTs heterostructure photocatalysts due to the delayed recombination of photogenerated electron-hole pairs. Moreover, surface oxidation state analysis demonstrates that Ce 3+ and Ce 4+ states coexist in CeO 2 , which enhance the separation of electron-hole pairs though cerium oxide shifting between CeO 2 and Ce 2 O 3 under photocatalytic process. In addition, the effects of the calcinating temperature, the molar ratio of ZnO to CeO 2 and the dosage of HNTs on photocatalytic activity of ZnO/CeO 2 @HNTs heterostructure photocatalysts were researched and the best possible values have been found. Furthermore, the photodegradation mechanism was systematically investigated by active species trapping experiment. It revealed that OH radicals play a little role while hole and O 2 − are the more major reactive species in the photodegradation process. [ABSTRACT FROM AUTHOR]

S-scheme heterojunction of In 2 O 3 /H 1.5 CN/2Au was prepared by hydrothermal, acidizing and calcination methods. The two-dimensional thin layer H 1.5 CN avoided the aggregation of In 2 O 3 and completed the S-scheme charge transfer with In 2 O 3. Moreover, Au not only enhanced the visible light absorption capacity of composites but also provided more active sites for CO 2 reduction. [Display omitted] • S-scheme heterojunction of In 2 O 3 /H 1.5 CN/2Au achieve CO 2 photocatalytic conversion to CO and CH 4. • The enhanced photocatalytic activity results from effective interfacial charge migration and separation and increased active sites. • The LSPR effect of Au improves the utilization of visible light. The construction of S-scheme heterojunction is of great significance for the photocatalytic reduction of CO 2. Here, we prepared two-dimensional (2D) ultra-thin g-C 3 N 4 by acidifying the carbon nitride precursor, and used In 2 O 3 to construct a S-scheme heterojunction with 2D g-C 3 N 4 , and finally In 2 O 3 /H 1.5 CN was modified with Au nanoparticles. The physicochemical properties of the prepared materials were studied by SEM/TEM, XPS, DRS, PL and photochemical test. Meantime, the S-scheme charge transfer mechanism was demonstrated by UPS and ESR. As a result, on the one hand, S-scheme heterojunction accelerated the transfer of electrons on the CB of In 2 O 3 to the VB of g-C 3 N 4 , avoided the recombination of photon-generated carrier. On the other hand, Au, as an effective cocatalyst, promoted photoinduced electron transfer and provided more active sites for CO 2 reduction and the local surface plasmon resonance phenomenon caused by Au NPs enhanced the visible light absorption capacity of the composite material. Moreover, 2D thin layer of g-C 3 N 4 played a carrier effect to disperse In 2 O 3 cube. Therefore, In 2 O 3 /H 1.5 CN/2Au had stable CO 2 reduction products, and the yields of CO/CH 4 reached 141.24/77.05 μmol/g. [ABSTRACT FROM AUTHOR]

The 15D/R achieve near 99.6% selectivity at the gas–solid interface for UV–Vis light-driven CO 2 reduction to CO, with a rate of 42.41 μmol·g−1. The high conductivity of RGO and the strong interaction with DUT-67 enhanced the electron coupling effect, which was conducive to the separation of carriers. The rapid formation of HCOO− and the rapid desorption of CO are responsible for the high CO yield and selectivity. [Display omitted] • The DUT-67/RGO aerogel are first prepared for CO 2 reduction in a gas–solid system. • 15D/R achieve near 99.6% selectivity for UV–Vis light-driven CO 2 reduction to CO. • Separation efficiency of carriers is the main reason for the improvement of CO yield. Herein, DUT-67/RGO aerogel photocatalysts with three-dimensional (3D) macroscopic morphology were first prepared by a facile hydrothermal and freeze-drying process. It was observed that DUT-67 endowed aerogels with strong adsorption/activation capacity for CO 2 molecules. Besides, RGO not only dispersed DUT-67 as a macroscopic carrier, but also improved the utilization rate of light energy. The high conductivity of RGO and the strong interaction with DUT-67 enhanced the electron coupling effect, which was conducive to the separation of carriers. 15D/R achieved near 99.6% selectivity at the gas–solid interface for UV–Vis light-driven CO 2 reduction to CO, with a rate of 42.41 μmol·g−1. The adsorption behavior of products at the interface and formation process of intermediates were monitored based on CO-TPD and in situ Fourier transform infrared spectra. The extremely high selectivity for CO came from the weak adsorption of CO on the surface of 15D/R and formation of CH 4 required more complex intermediates. [ABSTRACT FROM AUTHOR]

The 3D hierarchical structure of CdS/Ni-MOF inhibits the agglomeration of CdS, improve light harvesting, increase active surface area, reaction sites, promote charge transfer and separation, which greatly improves the efficiency of CO 2 conversion. However, when the CdS is overloaded and its hierarchical structure is destroyed, the heterostructure plays a major role in improving the performance. Based on the above results, we propose the preliminary mechanism of 20%-CdS/Ni-MOF photocatalytic reduction of CO 2. Firstly, under UV–Vis illumination, Ni-MOF and CdS are excited to produce electrons (e−) and holes (h+). Then, because of the tight interface contact, the e- excited by Ni-MOF could be transferred to CdS with more positive CB, and CdS as the active site could reduce CO 2 to CO more effectively. At the same time, the h+ in the VB of Ni-MOF and CdS participate in the oxidation reaction to produce O 2 and H 2 O 2 , which achieving the elimination of holes. Such charge separation and transfer of the electron-hole pairs facilitate enhanced photocatalytic activity. [Display omitted] • The 3D hierarchical heterostructure was synthesized by a simple strategy. • 20%-CdS/Ni-MOF showed excellent performance in the vapor–solid reaction system. • The hierarchical structure and heterostructure of CdS/Ni-MOF play a synergistic role. Fabricating the hierarchical heterostructure is efficient way for enhancing CO 2 conversion of semiconductor photocatalysts. Herein, a simple strategy has been employed to prepare several 3D hierarchical CdS/Ni-MOF heterostructure photocatalysts, and the selective photoreduction of CO 2 to CO under simulated sunlight in the gas–solid phase reactor. Among the prepared photocatalysts, 20%-CdS/Ni-MOF shows the best CO yield, which was 16 times and 7 times that of Ni-MOF and CdS, respectively. By controlling the morphology of the catalyst, we found that the significant improvement in photocatalytic activity can be ascribed to the synergistic effect of heterostructure in CdS/Ni-MOF and its unique hierarchical structure, which can improve the efficiency of charge transmission and provides abundant active sites, etc. Finally, the preliminary photocatalytic mechanism was discussed by in situ FTIR and liquid ultraviolet spectrophotometer. [ABSTRACT FROM AUTHOR]

rGO modified g-C 3 N 4 /R-CeO 2 Multi-interface contact S-scheme heterojunction photocatalyst maximizes the transfer efficiency of photogenerated electron and the CO 2 adsorption ability, thus greatly improving the CO 2 photoreduction performance. [Display omitted] • 2D-1D-2D g-C 3 N 4 /R-CeO 2 /rGO photocatalyst has been prepared for CO 2 photoreduction. • 2D-1D-2D multi-interface contact structure is of help for carrier transfer process. • π-π conjugation effect and Ce4+/Ce3+ transformation facilitate electron transmission. • In-situ FTIR and 13C isotope tracer tests analysis the CO 2 photoreduction mechanism. Construction of multi-interface contact step-scheme (S-scheme) photocatalyst is a promising pathway to achieve high-electron transfer efficiency for photocatalytic CO 2 reduction. In this paper, g-C 3 N 4 nanosheets were selected as the main photocatalyst, rod-like CeO 2 (R-CeO 2) with unique Ce4+→Ce3+ conversion property and rGO were loaded on the g-C 3 N 4 surface to construct 2D-1D-2D sandwich photocatalyst. The yields of CO and CH 4 were about 63.18 and 32.67 μmol/g after 4 h when the rGO/R-CeO 2 /g-C 3 N 4 was used as catalyst, which were about 4 and 6 times higher than that of pure CN, respectively. Cyclic experiments proved that the composite had excellent photocatalytic and material stability. Photoelectrochemical tests showed that the construction of S-scheme electron transfer model and the introduction of rGO can great enhance the electron transmission and separation of photogenerated electron-hole pairs. CO 2 adsorption test identified that the loading of R-CeO 2 and rGO obviously enhanced the CO 2 adsorption ability of pure g-C 3 N 4. Density functional theory (DFT) calculations used to analyze the electron transfer path and the formation of the build-in electric field at the semiconductor interface. In-situ FTIR and 13CO 2 element-tracer detection carried out to research the process of CO 2 photoreduction. A possible multi-interface contact S-scheme electron transfer mechanism for enhanced CO 2 photoreduction activity has been discussed. [ABSTRACT FROM AUTHOR]

Energy band location and charge separation mechanism of SnS 2 /Au/g-C 3 N 4 system during photoreduction under sunlight irradiation. • The catalyst is prepared by facile thermal treatment and chemical deposition method. • The SnS 2 /Au/g-C 3 N 4 composites show a superior optical adsorption under UV–vis light. • The Au nanoparticle and the Z-type scheme jointly improve the separation of carrier. • The SnS 2 /3ml-Au/g-C 3 N 4 displays the best photoreduction activity and durability. The use of semiconductor photocatalytic reduction technology has higher efficiency and lower energy consumption for CO 2 reduction, but its existence of some mismatched energy band positions and relatively slow charge-hole separation greatly limits its practical application. In this paper, a SnS 2 /Au/g-C 3 N 4 embedded structure model with carbon and nitrogen hybridization is proposed to gain an in-depth understanding of the role of hybridization and precious metal modification in photocatalysis. Carriers were investigated from the perspective of kinetics through photocurrent, LSV curve, and FL spectroscopy. After modification of Au nanoparticles, the photo-excited electrons showed a slower decay process, indicating that the separation of carriers was enhanced, which was further confirmed by impedance and PL spectroscopy. SEM, AFM and TEM analysis confirmed that the 2D face-to-face SnS 2 /Au/g-C 3 N 4 embedded structure was successfully prepared and the Au nanoparticles were evenly distributed. Au nanoparticles not only act as a bridge for electron transport in 2D semiconductor materials to accelerate electron transport, but generate more excited electrons by themselves under the radiation of sunlight, which effectively improves the separation efficiency of electron-hole pairs and enhances the photocatalyst activity. DFT calculations show that the Z-type mechanism and the intercalated energy level of the SnS 2 /Au/g-C 3 N 4 embedded structure expand the light absorption and improve the carrier separation efficiency. As expected, the photocatalyst activity with CO and CH 4 the evolution rate of up 93.81 µmol·g−1·h−1 and 74.98 µmol·g−1·h−1 under visible light irradiation, respectively, while the photocatalytic activity is negligible loss after 30 h photoreduction. This work reveals the role of embedded structure and precious metal modification in the separation and transmission of electron-hole, opening up new perspective for achieving high-efficiency solar CO 2 reduction performance. [ABSTRACT FROM AUTHOR]

Pt@CeO 2 /3DCN heterojunction are prepared by calcination method and photoreduction technology. The enhanced photoreduction of CO 2 performance can be ascribed to the synergistic effects of the oxygen vacancies in CeO 2 for CO 2 activation and heterojunction for electron separation. Besides, Pt nanoparticles (NPs) on CeO 2 /3DCN can further promote the transfer of electrons, resulting in higher photocatalytic activity. • The Pt@CeO 2 /3DCN photocatalyst was successfully synthesized. • Pt@45CeO 2 /3DCN exhibit best ability of CO 2 photoreduction under UV light. • The synergy of CeO 2 and 3DCN improves the photocatalytic performance. The conversion of CO 2 into high value-added carbon-based compounds through photocatalytic reduction technology is considered as one of the more promising strategies to solve the greenhouse effect. And construction of heterojunction photocatalysts can promote the separation of photoelectron-hole pairs, so as to achieve higher activity of photocatalytic CO 2 reduction. Hence, Pt@CeO 2 /3DCN heterojunction are prepared by calcination method and photoreduction technology. The photocatalytic results revealed that Pt@CeO 2 /3DCN show better photocatalytic activity for reducing CO 2 into CO and CH 4 , compared with 3DCN. Especially, Pt@45CeO 2 /3DCN shows the maximum photocatalytic activity of 4.69 and 3.03 μmol·h−1·g−1 for CO and CH 4 under UV light irradiation, respectively, and the reduction activity did not decrease significantly after five cycles. The enhanced photoreduction of CO 2 performance can be ascribed to the synergistic effects of the oxygen vacancies in CeO 2 for CO 2 activation and heterojunction for electron separation. Besides, Pt nanoparticles (NPs) on CeO 2 /3DCN can further promote the transfer of electrons, resulting in higher photocatalytic activity. [ABSTRACT FROM AUTHOR]